Field of the Invention
The present invention relates to a thermostat having a hollow body, wherein the hollow body is at least partly filled with a thermosensitive medium, wherein a heating element is provided for heating the thermosensitive medium.
Description of the Background Art
Cooling systems in motor vehicles can include an internal combustion engine, a heat exchanger, a circulating pump, and a control element, among other items. The control element in these systems can influence the flow of a coolant through the components as a function of the temperature of the coolant. In this context, flow through the heat exchanger in particular, which is often designed as a radiator, is influenced by the control element. The control element can be composed of a thermostat valve in this context.
A thermostat valve in these systems can have an expansion element that causes a displacement of an actuator as a result of a temperature-dependent volume expansion of a temperature-sensitive medium. The position of the actuator influences the flow path of the coolant within the cooling system.
Customarily, the thermosensitive media for a thermostat are designed on the basis of the operating conditions and the associated heat generation of the internal combustion engine.
Especially in operating states of the internal combustion engine in which only a partial load is required from the internal combustion engine, excessive cooling of the internal combustion engine can occur, resulting in a non-optimal operating temperature of the internal combustion engine.
Electrically heatable thermostat valves were developed in order to deal with this problem. Such thermostat valves are also referred to as map-controlled thermostat valves. So-called PTC elements (positive temperature coefficient elements) can be used for heating, for example. As a result of the electrical heating, the phase transition of the thermosensitive material can take place independently of the temperature of the coolant within certain limits, especially in operation at full load.
The document DE 101 10 185 A1, which corresponds to U.S. Pat. No. 7,172,133 (B2), and which discloses an electrically heatable thermostat valve, for example. In this design, a heating element is mounted on a plastic base. The electrical contacts here are passed through the base. The base itself is inserted into the container that holds the thermosensitive medium.
It is a particular disadvantage of the prior art solutions that sealing the container that holds the thermosensitive medium is difficult. This is true for both the interface between the container and the base and for the feed-throughs for the electrical contacts in the base or in the container.